This invention relates to the radio-labelling of proteins and is specifically concerned with the labelling of monoclonal antibodies and other proteins with .sup.32 P. The term "protein" as used herein encompasses polypeptides.
The concept of using monoclonal antibodies, and other proteins as delivery vehicles for the targeting of drugs is already established. Practical difficulties exist however when it comes to attaching the drug to the monoclonal antibody or other delivery system since this must be done in such a way that the activity of the drug is retained and, at the same time, the specificity of the monoclonal antibody or other delivery system is maintained. At a practical level, this places considerable restriction upon those chemical and biological methods theoretically available for the linking of the drug to the delivery system as many conventional reaction conditions will destroy either or both of the drug activity and delivery system specificity.
Radiation therapy is now well-established as one possible method of treatment of certain cancer conditions and the attachment of the radio-isotopes of iodine and a variety of metals, e.g. indium and yttrium to antibodies is currently being investigated for this purpose. The radionuclide .sup.32 P is, in many ways, a particularly advantageous radionuclide for use against certain types of solid tumours with relatively poor blood supply since .sup.32 P has a reasonably short half-life of 14 days and it is a pure beta-emitter with a particle energy of 1.7 MeV. However, it has not been possible to attach .sup.32 P to antibodies by the methods that have been used previously for the attachment of other radio-isotopes.